1. Field of Invention
This invention relates to a remote sensing device that is used to detect and measure particulate matter emissions from vehicles.
2. Description of Related Art
Remote sensing of vehicle exhaust has been shown to be an economical method to determine on-road emissions for thousands of vehicles per day.
A Remote Sensing Device (RSD) is placed on the side of a one-lane road, often a freeway onramp. It measures the gaseous emissions of individual passing vehicles. The main gases of interest are carbon monoxide (CO), hydrocarbons (HC), nitrous oxides (NOx), and carbon dioxide (CO2) as exhaust plume dilution tracer. For example, the Fuel Efficiency Automobile Test (FEAT) system uses absorption measurements in the infrared and ultraviolet spectral regions to determine column concentrations of CO, CO2, HC, and NO in the exhaust plume of each passing vehicle. By determining the ratio of CO, HC, and NO to CO2, emission factors (per unit fuel consumption) can be derived. Remote sensing devices may also employ ancillary devices to register speed, acceleration, and the license plate for each passing vehicle. These data help with the further interpretation and use of the measurements of gaseous emissions. The practical and commercial applications of the remote sensing devices for gaseous emissions are currently mainly in three areas:
1. Gross Emitter Identification: Vehicles with emissions of gaseous pollutants exceeding emission standards are identified. Vehicle owners are notified and required to bring the vehicle into compliance with emission standards.
2. Clean Screening: Vehicles with emissions of gaseous pollutants in compliance with emission standards are identified. Vehicle owners are notified that they have passed the smog check and can reregister their vehicle after paying the usual inspection and maintenance fee. Part of this fee funds the remote sensing program.
3. Evaluation of Fleet Emissions: The statistical distribution of emission rates over different vehicle fleets is evaluated with remote sensing. This information is valuable from a scientific point of view and important for areas in non-attainment with air quality standards to devise a plan (e.g., state implementation plan) to come into compliance in a cost-effective manner.
In addition to gaseous pollutants, there is interest in developing remote sensing methods for measuring on-road particulate matter emissions from vehicles. Measurements of particulate matter mass emissions from the tail-pipes of vehicles can be made on a dynamometer with direct collection onto filters. However, this method is orders of magnitudes more expensive than on-road remote sensing measurements and only small numbers of vehicles have been tested. This is due to the need of pulling vehicles over and testing them individually on a (portable) dynamometer. Therefore, only a small fraction of the vehicles passing by can be tested.
On-road measurements of light absorbing particle emissions have been made both with an aethalometer and with the University of Denver (DU) opacity method. Both methods, as implemented, are only sensitive to the black carbon (BC) mass component of particulate mass emissions. For gasoline combustion engines, particulate mass emissions are generally dominated by organic carbon (OC) mass, while for diesel engines either BC or OC can be the dominant component. In addition, aethalometer measurements cannot assign emissions to single vehicles in dense traffic, and the DU method is relatively insensitive and cannot distinguish between road-dust opacity and exhaust opacity. Road dust opacity can be a significant part of the total opacity, especially if the remote sensor makes measurements near the road surface level as commonly done for vehicles with tailpipes mounted below the main vehicle body. The in-situ aethalometer technique relies on collecting a plume sample and therefore must be located down-wind of the traffic flow, so that the exhaust plume is transported to the instrument inlets. This makes site selection much more difficult and often reduces the probability of a successful measurement.
The University of Denver (DU) opacity method uses the reference channel of a conventional RSD to measure infrared light extinction due to particles. This method yields only extinction values integrated across the road and is therefore not capable of distinguishing between tail pipe particle emissions and entrained road dust. As currently implemented (i.e., using infrared light), this method is also only sensitive to the black carbon (BC) mass component of particulate mass emissions. For gasoline combustion engines, particulate mass emissions are generally dominated by organic carbon (OC) mass, while for diesel engines either BC or OC can be the dominant component. In addition, the DU method is relatively insensitive as it measures an often small departure from the background signal of the reference beam.
What has long been needed is a sensor to measure particulate mass in a remote sensing device that can distinguish between road-dust particles and exhaust particles. Another long felt need is for a particulate sensor that also measures both black carbon particles and organic carbon particles. Another long felt need is for a particulate sensor that can measure particulate levels from multiple vehicles in dense traffic.
1. Advantages of the Invention
An advantage of the present invention is that it provides a particle measurement system for particles emitted in the exhaust gas of a vehicle.
Another advantage of the present invention is that it provides a vehicle particulate sensor that can discriminate between road dust and particles emitted by the vehicle.
A further advantage of the present invention is that it provides a vehicle particulate sensor that can quickly and easily be deployed by at a roadside location.
An additional advantage of the present invention is that it provides a vehicle particulate sensor that can measure the particulate emissions from multiple vehicles as they pass a test site.
Yet another advantage of the present invention is that provides a measurement of particulate emissions that can be combined for each vehicle with a measurement of carbon dioxide emissions. Thereby, a ratio of particulate emissions per volume of fuel can be calculated.
An advantage of the present invention is that it provides a vehicle particulate sensor that can detect both organic carbon and black carbon particles.
An additional advantage of the present invention is that it provides a vehicle particulate sensor that is insensitive to effects from visible light.
These and other advantages of the present invention may be realized by reference to the remaining portions of the specification, claims, and abstract.
2. Brief Description of the Invention
The present invention comprises an apparatus for measuring particles in a gas. A transmitter is adapted to provide a source of ultraviolet radiation. The radiation travels through the gas and impinges upon the particles in the gas generating a backscattered radiation. The transmitter also generates a timing signal. A receiver is located in proximity of the transmitter. The receiver is adapted to receive the backscattered radiation and to generate a backscattered signal indicative of the quantity of particles entrained in the gas. A data system is connected to the receiver, the data system is adapted to receive the timing signal and the backscattered signal as an input and to calculate a quantity of particles in the gas at a location from the transmitter.
The above description sets forth, rather broadly, the more important features of the present invention so that the detailed description of the preferred embodiment that follows may be better understood and contributions of the present invention to the art may be better appreciated. There are, of course, additional features of the invention that will be described below and will form the subject matter of claims. In this respect, before explaining at least one preferred embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of the construction and to the arrangement of the components set forth in the following description or as illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.